The rapid increase in the popularity and use of cellular and satellite communications systems has highlighted the impeding congestion of mobile communications spectrum. Concurrently, rapid advances in digital signal processing technology have made possible the transmission of voice signals at ever decreasing encoding rates. This latter development is permitting the transmission of speech to be realized over much narrower channel bandwidths, thus promising to increase the system's subscriber capacity proportionally to the potential bandwidth requirements reduction (e.g., five-fold). These two developments have permitted mobile networks to be converted from analog-based systems to digital-based systems.
Unfortunately, the digitization of new mobile networks has made the transparent support of non-voice traffic impossible without the development of specialized interworking functions, which are tailored to specific end-user applications.